This is a note to let you know that I've just added the patch titled
net: let net.core.dev_weight always be non-zero
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-let-net.core.dev_weight-always-be-non-zero.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 709e1d4e509f9e125c8ffcc57f86a6530985205c
Author: Liu Jian <liujian56@xxxxxxxxxx>
Date: Thu Jan 16 22:30:53 2025 +0800
net: let net.core.dev_weight always be non-zero
[ Upstream commit d1f9f79fa2af8e3b45cffdeef66e05833480148a ]
The following problem was encountered during stability test:
(NULL net_device): NAPI poll function process_backlog+0x0/0x530 \
returned 1, exceeding its budget of 0.
------------[ cut here ]------------
list_add double add: new=ffff88905f746f48, prev=ffff88905f746f48, \
next=ffff88905f746e40.
WARNING: CPU: 18 PID: 5462 at lib/list_debug.c:35 \
__list_add_valid_or_report+0xf3/0x130
CPU: 18 UID: 0 PID: 5462 Comm: ping Kdump: loaded Not tainted 6.13.0-rc7+
RIP: 0010:__list_add_valid_or_report+0xf3/0x130
Call Trace:
? __warn+0xcd/0x250
? __list_add_valid_or_report+0xf3/0x130
enqueue_to_backlog+0x923/0x1070
netif_rx_internal+0x92/0x2b0
__netif_rx+0x15/0x170
loopback_xmit+0x2ef/0x450
dev_hard_start_xmit+0x103/0x490
__dev_queue_xmit+0xeac/0x1950
ip_finish_output2+0x6cc/0x1620
ip_output+0x161/0x270
ip_push_pending_frames+0x155/0x1a0
raw_sendmsg+0xe13/0x1550
__sys_sendto+0x3bf/0x4e0
__x64_sys_sendto+0xdc/0x1b0
do_syscall_64+0x5b/0x170
entry_SYSCALL_64_after_hwframe+0x76/0x7e
The reproduction command is as follows:
sysctl -w net.core.dev_weight=0
ping 127.0.0.1
This is because when the napi's weight is set to 0, process_backlog() may
return 0 and clear the NAPI_STATE_SCHED bit of napi->state, causing this
napi to be re-polled in net_rx_action() until __do_softirq() times out.
Since the NAPI_STATE_SCHED bit has been cleared, napi_schedule_rps() can
be retriggered in enqueue_to_backlog(), causing this issue.
Making the napi's weight always non-zero solves this problem.
Triggering this issue requires system-wide admin (setting is
not namespaced).
Fixes: e38766054509 ("[NET]: Fix sysctl net.core.dev_weight")
Fixes: 3d48b53fb2ae ("net: dev_weight: TX/RX orthogonality")
Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
Link: https://patch.msgid.link/20250116143053.4146855-1-liujian56@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 586598887095d..b3b39b0e0745b 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -242,7 +242,7 @@ static int proc_do_dev_weight(struct ctl_table *table, int write,
int ret, weight;
mutex_lock(&dev_weight_mutex);
- ret = proc_dointvec(table, write, buffer, lenp, ppos);
+ ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
if (!ret && write) {
weight = READ_ONCE(weight_p);
WRITE_ONCE(dev_rx_weight, weight * dev_weight_rx_bias);
@@ -356,6 +356,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "dev_weight_rx_bias",
@@ -363,6 +364,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "dev_weight_tx_bias",
@@ -370,6 +372,7 @@ static struct ctl_table net_core_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_do_dev_weight,
+ .extra1 = SYSCTL_ONE,
},
{
.procname = "netdev_max_backlog",
